The National Institute of Mental Health Panic Disorder Questionnaire (NIMH-PQ) has been developed by the Section on Anxiety and Affective Disorders to assess special clinical and life-course-of-illness variables in patients with putative or DSM-III-R validated panic disorder. The SAAD has demonstrated that this instrument has good validity on items that it shares with the SADS-L. Data collected in over 1000 patients with putative panic disorder are being analyzed in terms of the phenomenology and longitudinal course of panic disorder patients with versus without sleep panic attacks or agoraphobia. Preliminary findings in this clinical sample indicate that agoraphobia without panic attacks is a rare or nonexistent syndrome. Patients with sleep panic attacks appear to be at increased risk for developing relaxation-induced and sleep-deprivation-induced panic attacks compared with panic disorder patients without sleep panic attacks. The time-to-peak intensity of panic attacks may not be a valid construct for the diagnosis of panic attacks in panic disorder patients.